1. Field of the Invention
The present invention relates to a lighting device, using light-emitting diodes, intended to be used inside motor vehicles.
2. Description of the Related Art
The field of the invention is, in general terms, that of lighting and signalling applied to motor vehicles. Within this field, various types of devices are known using light-emitting diodes, or LEDs, including basically the following devices:                lighting devices located at the rear of the vehicle with, in particular, reversing lights;        signalling devices located at the front (or on the side) of the vehicle with, in particular, direction indicators, repeat flash lights and DRLs (daytime running lights);        signalling devices located at the rear of the vehicle with, in particular, fog lights, rear lights, direction indicators and stop lights, “upper stop” lights;        internal lighting devices with, in particular, the main roof lamps (front, central, rear), or cigarette lighter illuminating modules; raised stop light-type rear lights, usually arranged in a central upper portion of the central rear windscreen, also belong to the category of internal lighting devices;        internal or external lighting devices contributing to style, with for example style lines illuminated on the mudguards of the vehicle or on the dashboard, the door trimmings or else lighting of the body roof.        
In the past, for all of these devices, use has traditionally been made of conventional lamp-type light sources or optionally of halogen lamps. However, over recent years, motor vehicle equipment manufacturers have proposed the use of LEDs, in particular for signalling lights. Light-emitting diodes have a certain number of advantages:                firstly, it has long been known that diodes of this type do not radiate omnidirectionally but rather radiate within a half-space remote from a substrate supporting the PN junction of the diode in question; thus, by using more directional radiation than the halogen, or discharge, lamps of the prior art, less power is lost than with discharge or halogen lamps;        then, these diodes were gradually improved in terms of radiation intensity; they can now radiate a flux of approximately 100 lumens. Moreover, the manufactured diodes have long emitted radiation in the red range, but now also in the white range, thus broadening the field of their conceivable uses. The amount of heat that they release is relatively low, and a certain number of constraints, associated with the dissipation of heat in the headlamp devices of the prior art, have disappeared;        finally, diodes consume less power, even at the same radiation intensity, than discharge lamps or halogen lamps; they have a low overall size and their particular shape provides new possibilities for production and arrangement on complex surfaces for which they are intended.        
Generally, light-emitting diodes are arranged on a substrate-type support (the best-known ones within the motor vehicle field being the SMI, FR4, CEM1, etc. substrates) which is, according to a general definition, a material intended to receive the imprint of an electronic circuit, and/or the various components forming this circuit, all of this forming a PCB (printed circuit board). A distinction can now be drawn, in particular, between three types of diodes; what are known as axial emission diodes, which emit a light beam in a main direction substantially perpendicular to the plane of the PCB supporting them, lateral emission diodes, which emit a light beam in a direction parallel to the PCB supporting them, and through-emission diodes, known as reverse gullwing diodes, which emit light through the PCB.
The present invention relates specifically to internal lighting devices. In the prior art, each internal lighting function, and more specifically each internal lighting function using light-emitting diodes, is performed using a specific lighting device dedicated exclusively to this function. Most of the functions in question correspond to a specific situation of life on board, such as reception, driving or else rest. The fact that there is a specific lighting device entails considerable costs in the performance of the internal lighting functions.
A general problem that the invention seeks to solve is thus a problem of reducing costs in the performance of the various internal lighting functions.